Depends on the specific weight distribution of the object to be hung.
I saw girls at a strip club using a uh…toy, in a shower room once.
It appeared to have a lot of weight suspended from it. The single suction cup, held up marvelously.
Conversely. I think something with it’s weight closer to the wall/surface, would benefit more from multiple cups. Like a shower mirror.
That being said, a toilet plunger is capable of tremendous suction. Most models have a single suction design.
I would say that the material comprising the cups, and the surface’s material and texture.
Temperature can be a variable.
The Sun will “unlock” some suction cup stuff from car windows…
I feel like freezing would mess up suction as well. Potentially.